The invention relates to mobile radio-communication systems and more particularly to the positioning of mobile units.
In prior art systems, base stations are equipped with smart antennas. Currently, the most advanced smart antenna is an adaptive antenna which may also be referred to as an adaptive array antenna. Adaptive array antennas facilitate the measuring of a direction of an incoming signal. Such antennas also enable the device to which they are connected to control the direction in which signals are transmitted thereby optimizing the power required for signal transmission.
Adaptive array antennas are often used to obtain positioning information regarding the location of mobile units. Multipath, however, between a mobile unit and a base station often results in inaccurate positioning of mobile units. Where multipath is present, either at the mobile unit or the base station or both, accurate positioning of mobile units is often difficult or impossible to measure.
It would therefore be desirable to accurately position mobile units despite the presence of multipath and to more accurately position mobile units where multipath is not present.